diff -r 0b78a8c35357 Doc/library/smtplib.rst
--- a/Doc/library/smtplib.rst	Thu Dec 15 18:58:35 2016 -0500
+++ b/Doc/library/smtplib.rst	Sun Dec 18 21:47:08 2016 -0500
@@ -496,7 +496,7 @@
    specified in :rfc:`5322`\: *from_addr* is set to the :mailheader:`Sender`
    field if it is present, and otherwise to the :mailheader:`From` field.
    *to_addrs* combines the values (if any) of the :mailheader:`To`,
-   :mailheader:`Cc`, and :mailheader:`Bcc` fields from *msg*.  If exactly one
+   :mailheader:`Cc`, and :mailheader:`Bcc` fields from *msg*.  If a
    set of :mailheader:`Resent-*` headers appear in the message, the regular
    headers are ignored and the :mailheader:`Resent-*` headers are used instead.
    If the message contains more than one set of :mailheader:`Resent-*` headers,
diff -r 0b78a8c35357 Lib/smtplib.py
--- a/Lib/smtplib.py	Thu Dec 15 18:58:35 2016 -0500
+++ b/Lib/smtplib.py	Sun Dec 18 21:47:08 2016 -0500
@@ -912,21 +912,20 @@
         # 'Resent-Date' is a mandatory field if the Message is resent (RFC 2822
         # Section 3.6.6). In such a case, we use the 'Resent-*' fields.  However,
         # if there is more than one 'Resent-' block there's no way to
-        # unambiguously determine which one is the most recent in all cases,
-        # so rather than guess we raise a ValueError in that case.
-        #
-        # TODO implement heuristics to guess the correct Resent-* block with an
-        # option allowing the user to enable the heuristics.  (It should be
-        # possible to guess correctly almost all of the time.)
+        # unambiguously determine which one is the most recent in all cases.
+        # See RFC 5322 section 3.6.6, first paragraph for more details about the
+        # "should" that the code should respect.
 
-        self.ehlo_or_helo_if_needed()
-        resent = msg.get_all('Resent-Date')
-        if resent is None:
-            header_prefix = ''
-        elif len(resent) == 1:
-            header_prefix = 'Resent-'
-        else:
+        if [ header[0] for header in msg._headers ].count('Resent-Date') > 1:
             raise ValueError("message has more than one 'Resent-' header block")
+
+        #Resent or original?
+        header_prefix = 'Resent-' if len(msg.get('Resent-Date','')) >= 1 else ''
+        
+        # RFC 5322 section 3.6, 4th Paragraph
+        if msg.get('Date',None) is None:
+            msg['Date'] = email.utils.formatdate()
+
         if from_addr is None:
             # Prefer the sender field per RFC 2822:3.6.2.
             from_addr = (msg[header_prefix + 'Sender']
@@ -1110,5 +1109,6 @@
 
     server = SMTP('localhost')
     server.set_debuglevel(1)
-    server.sendmail(fromaddr, toaddrs, msg)
+    #server.sendmail(fromaddr, toaddrs, msg)
+    server.send_message(from_addr=fromaddr, to_addrs=toaddrs, msg=email.message_from_string(msg))
     server.quit()
diff -r 0b78a8c35357 Lib/test/test_smtplib.py
--- a/Lib/test/test_smtplib.py	Thu Dec 15 18:58:35 2016 -0500
+++ b/Lib/test/test_smtplib.py	Sun Dec 18 21:47:08 2016 -0500
@@ -531,22 +531,38 @@
                                  re.MULTILINE)
             self.assertRegex(debugout, to_addr)
 
-    def testSendMessageMultipleResentRaises(self):
+    def testSendMessageMultipleResent(self):
+        first_date = 'Thu, 1 Jan 1970 17:42:00 +0000'
+        first_from = 'holy@grail.net'
+        first_to  = 'Martha <my_mom@great.cooker.com>, Jeff'
         m = email.mime.text.MIMEText('A test message')
         m['From'] = 'foo@bar.com'
         m['To'] = 'John'
         m['CC'] = 'Sally, Fred'
         m['Bcc'] = 'John Root <root@localhost>, "Dinsdale" <warped@silly.walks.com>'
-        m['Resent-Date'] = 'Thu, 1 Jan 1970 17:42:00 +0000'
-        m['Resent-From'] = 'holy@grail.net'
-        m['Resent-To'] = 'Martha <my_mom@great.cooker.com>, Jeff'
         m['Resent-Bcc'] = 'doe@losthope.net'
         m['Resent-Date'] = 'Thu, 2 Jan 1970 17:42:00 +0000'
         m['Resent-To'] = 'holy@grail.net'
         m['Resent-From'] = 'Martha <my_mom@great.cooker.com>, Jeff'
+        m._headers.insert(0,m.policy.header_store_parse('Resent-Date', first_date))
+        m._headers.insert(0,m.policy.header_store_parse('Resent-From', first_from))
+        m._headers.insert(0,m.policy.header_store_parse('Resent-To', first_to))
+
         smtp = smtplib.SMTP(HOST, self.port, local_hostname='localhost', timeout=3)
         with self.assertRaises(ValueError):
-            smtp.send_message(m)
+            smtp.send_message(m) #Raise an error at the moment
+        self.assertEqual(first=m.get('Resent-Date'),
+                         second=first_date,
+                         msg="""
+                             The Resent-Date order is not read correctly or
+                             something wrong happened.
+                             """)
+        self.assertEqual(first=m.get('Resent-From'),
+                         second=first_from,
+                         msg="""
+                             The Resent-From order is not read correctly or
+                             something wrong happened.
+                             """)
         smtp.close()
 
 class NonConnectingTests(unittest.TestCase):